[LTO] Make sure we flush buffers to work around linker shenanigans.

lld, at least, doesn't call global destructors by default (unless
--full-shutdown is passed) because it's, allegedly, expensive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294953 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed